Motivation:

Followed the study on drupal.star.bnl.gov/STAR/blog/yili/underlying-event-activity-pp-200-gev-2015-09-28-2   (R=0.4, Dijet required, HIgh Tower trigger)

Here R = 0.6, at least one jet, Jet patch trigger

 

How does underlying event multiplicity, average pT change with Leadiing jet pT?

CMS publication: arxiv.org/abs/1507.07229


CDF publication: arxiv.org/abs/1508.05340

Grant Webb's study on p+p 500 GeV data: drupal.star.bnl.gov/STAR/blog/gdwebb/underlying-event-run-9-pp-500-gev
Zilong Change's study on PYTHIA p+p 500 GeV: drupal.star.bnl.gov/STAR/blog/zchang/underlying-event-study-4

Here is Li Yi's third step to study the underlying event in p+p 200 GeV. 


See Master Page: drupal.star.bnl.gov/STAR/blog/yili/master-page-underlying-event-pp-200-gev

Data:

p+p 200 GeV
Run 12 
filetype=daq_reco_MuDst,events!=0,trgsetupname=pp200_production_2012,filename~st_physics,production=P13ib,storage!=hpss,sanity=1

triggerid: 370601, 370611, 370621
for JP0, JP1, JP2

Cuts:

|Vz|<30 cm
|eta|<1
|dca|< 1 cm 
NFIt > 20 points
NFit/NFitPossible > 0.52
Track Pt or Tower Et<1000GeV

no pileup removal

anti-kT algorithm
R = 0.6
ghost area 0.01

14M events, found 2.3 M jet events (no jet pT requirement) 

Method:

1. Search for jet, identify jet φ_jet
Both TPC tracks and BEMC towers are used for jet reconstruction by fastjet pacakge.  

2. Loop over tracks (charged particles only) 

|φ-φ_jet|<60 degree --> Leading jet direction
|φ-φ_jet|>120 degree --> "SubLeading" jet direction
60 degree<|φ-φ_jet|<120 degree --> transverse direction

For the two transverse directions, the one with larger pT sum of the charged particle is defined as TranMax. The other is TranMin. 

3. Sum the multiplciity in various directions.
Calucate the average pT in various directions. 

Result: